THE VISCERAL MASS IN ANTEDON ROSACEUS. 303 



starvation, the whole alimentary canal being, of course, removed. In 

 order to avoid this danger we may imagine that the visceral mass at 

 this period becomes more firmly attached to the calyx. If this view 

 be correct, we must suppose that the loss of the visceral mass is by no 

 means an uncommon occurrence amongst Comatulce, and I am strongly 

 inclined to believe that such is the case. What is the meaning of 

 this process, and whether it plays any special part in the economy of 

 the animal must for the present remain undecided ; I have, however, 

 thrown out a suggestion on this point at the end of the paper. 



Effects of Evisceration. — Eemoval of the visceral mass appears 

 to affect the animals but little. At first they fold their arms over the 

 calyx, but this condition does not generally last for long, and in an 

 hour or two, when they have once recovered from the shock, their 

 vigour seems to be unimpaired. 



It is evident that evisceration involves tearing of the epidermis and 

 dermis, which together form the oral perisome, in a more or less 

 regular circle all round where the arms join on to the disc, and that 

 the ambulacral grooves and nerves, together with the ambulacral 

 vessels, must also be torn across. The central plexus of blood vessels 

 must also be broken across at some part of its course. The visceral 

 mass, as it appears after its removal from the calyx, has been already 

 described. Isolated specimens of the visceral mass of one species of 

 Comatula, dredged on the Challenger expedition, were observed by Sir 

 Wy ville Thomson to perform slow creeping movements ; x but I have 

 noted nothing of the sort in Antedon rosaceus — on the contrary, the 

 visceral masses appeared to remain quite still, and slowly decay. 



The central capsule, together with the nerves radiating from it to 

 the arms, is uninjured by the operation. It will be convenient for 

 purposes of reference to speak of the shallow, empty cup, left by the 

 removal of the visceral mass, as the "visceral basin." 



The earlier stages in the process of regeneration will perhaps be 

 rendered clearer if I first of all give a somewhat more particular 

 account of the appearance presented by a freshly eviscerated specimen. 

 The following description is taken from a specimen which was dredged 

 in the eviscerated condition, but will apply equally well to a specimen 

 upon which the operation has been intentionally and successfully 

 performed. The line of tear, along which the oral perisome has been 

 1 Challenger Report, Nan: of Cruise, vol. L, Pt. I., p. 311. 



